class Solution {
public:
    int minPathSum(vector<vector<int>>& grid) {
        int m = grid.size();
        if(m == 0) return 0;
        int n = grid[0].size();
        if(n == 0) return 0;
        vector<int> t(n, 0x7fffffff);
        vector<vector<int>> dp(m,t);
        dp[0][0] = grid[0][0];
        for(int i = 1 ; i < n; ++i){
            dp[0][i] = dp[0][i-1] + grid[0][i];
        }

        for(int i = 1 ; i < m; ++i){
            dp[i][0] = dp[i-1][0] + grid[i][0];
        }

        for(int i = 1 ; i < m; ++i){
            for(int j = 1; j < n; ++j){
                dp[i][j] = min(dp[i-1][j] + grid[i][j], dp[i][j-1] + grid[i][j]);
            }
        }
        return dp[m-1][n-1];
    }
};